1. Field of the Invention
The present invention relates to an Alternating Current/Direct Current (AC/DC) converter for converting a commercial Alternating Current (AC) voltage into a Direct Current (DC) voltage.
2. Description of the Related Art
Electronic apparatus, such as personal computers, television sets, and video recorders, operate by using an external AC voltage as power. An electronic apparatus of this kind has an AC/DC converter built in for performing AC/DC conversion on a commercial AC voltage, or an external power adapter (AC power adapter) including the AC/DC converter.
FIG. 1 is a circuit diagram illustrating the structure of a power adapter 100r on which the inventors' research was based. The power adapter 100r of FIG. 1 is an AC/DC converter for converting an AC voltage VAC into a DC voltage VDC, which includes a concentric plug 102, a discharge resistor R1, a filter circuit 10, a rectifier and smoothing circuit 20, a Direct Current/Direct Current (DC/DC) converter 30r, and an apparatus side connector 106.
When inserted into a socket 2 of an insertion connector for wiring, the concentric plug 102 receives the commercial AC voltage VAC. The filter circuit 10 removes noise of the commercial AC voltage VAC. A diode bridge circuit 22 of the rectifier and smoothing circuit 20 performs full-wave rectification on the AC voltage VAC of the filter circuit 10. A smoothing capacitor C21 of the rectifier and smoothing circuit 20 smooths the voltage rectified by the diode bridge circuit 22.
The DC/DC converter 30r converts a voltage level of a smoothed DC voltage VIN. The DC voltage VDC stabilized at a certain voltage level by the DC/DC converter 30r is supplied to an electronic apparatus 1 through the apparatus side connector 106. The discharge resistor R1, the filter circuit 10, the diode bridge circuit 22, the smoothing capacitor C21, and the DC/DC converter 30r are built in a frame body 104 of the power adapter 100r. The connection between the frame body 104 and the concentric plug 102 and the connection between the frame body 104 and the apparatus side connector 106 are achieved respectively through cables.